Acetals derived from ketones by replacement of the oxo group by two hydrocarbyloxy groups R2C(OR)2 ( RH ). This term, once abandoned, has been reinstated as a subclass of acetals.
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1345